China Animal Husbandry and Veterinary Medicine ›› 2025, Vol. 52 ›› Issue (4): 1567-1578.doi: 10.16431/j.cnki.1671-7236.2025.04.011

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Effects of Rumen-protected Methionine Supplementation in Diets with Different Protein Levels on Growth Performance,Rumen Fermentation and Apparent Digestibility of Nutrients in Yaks

LAI Qiushuang1, LI Lingshuo1, LI Shuyi1, TIAN Wei2, YU Qingting2, ZHANG Kanglin2, LI Depeng1, LIU Jun2, JIANG Fei1, PENG Zhongli1, WU Jianping2, HUANG Yanling1   

  1. 1. College of Animal Science and Veterinary Medicine of Southwest Minzu University, Chengdu 610041, China;
    2. Institute of Animal Husbandry Scienc, Ganzi Tibetan Autonomous Prefecture, Kangding 626000, China
  • Received:2024-10-28 Published:2025-03-29

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Abstract: 【Objective】 This experiment aimed to explore the effects of supplementing rumen-protected methionine (RPM) to diets with different protein levels on the growth performance,rumen fermentation and nutrient apparent digestibility of yaks,so as to provide a reference for dietary protein level and RPM supplementation of house-feeding yaks breeding.【Method】 A 2×3 two-factor experimental design was adopted in this experiment.Two protein levels were low (13%) and high (15%),and three RPM levels were 0,0.05% and 0.10%.A total of thirty-six 4-year-old healthy male yaks with similar body weight (225.29 kg±30.59 kg) and body size were selected and randomly divided into six treatment groups.Each treatment group had six replicates,and each replicate had one yak.Single pen and single feeding were adopted.The pre-trial period was 10 d,followed by a formal trial period of 60 d.Samples of feed,faeces and rumen fluid were collected on 66-69 and 70 d of experiment for determining the growth performance,apparent digestibility of nutrients and rumen fermentation parameters of yaks.【Result】 ①Dietary protein levels had no significant effect on average daily dry matter intake (ADMI) of yaks (P＞0.05),but compared with 13% protein group,average daily gain (ADG) of yaks in 15% protein group was significantly higher (P＜0.05), and feed to gain ratio (F/G) was significantly lower (P＜0.05).The RPM supplementation had no significant effect on ADMI and F/G (P＞0.05),but tended to increase ADG (P＝0.051).There was a trend of interaction between dietary protein levels and RPM levels on ADMI in yaks (P＝0.058).②Dietary protein levels had no significant effect on rumen pH and microbiological proteins (MCP) (P＞0.05),but had a tendency to increase the content of NH3-N (P＝0.091).There was no significant effect of dietary RPM levels on rumen pH,MCP and NH3-N (P＞0.05).There was a trend of interaction between dietary protein levels and RPM levels on rumen NH3-N content in yak (P＝0.092).Compared with 13% protein group, content of propionic acid was higher (P＜0.05),the content of butyric acid (P＝0.066),isobutyric acid (P＝0.073),valeric acid (P＝0.053) and isovaleric acid (P＝0.056) had a tendency to increase in 15% protein group.There was no significant effect of dietary RPM levels on rumen volatile fatty acids (P＞0.05).There was no significant interaction to volatile fatty acid between dietary protein levels and RPM levels (P＞0.05).③Compared with 13% protein group,apparent digestibility of crude protein,calcium and acid detergent fiber in 15% protein group was significantly increased (P＜0.05).There was no significant effect of dietary RPM levels on nutrient apparent digestibility (P＞0.05).There was no significant interaction to nutrients apparent digestibility between dietary protein levels and dietary RPM levels (P＞0.05).【Conclusion】 Under the conditions of this experiment,adding 0.05% rumen protected methionine to the diet with a 15% protein level for 4-year-old house-fed yaks could improve their rumen fermentation,increase their dry matter intake,nutrient apparent digestibility and growth performance.

Key words: yak; protein level; rumen-protected methionine; growth performance; rumen fermentation; nutrient apparent digestibility

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